package com.yieldnull.httpd;

import com.yieldnull.httpd.mime.MimeUtility;

import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

/**
 * Entity Header
 */
class MultipartHeader {

    private final Map<String, List<String>> headerNameToValueListMap = new LinkedHashMap<>();

    public String getHeader(String name) {
        String nameLower = name.toLowerCase(Locale.ENGLISH);
        List<String> headerValueList = headerNameToValueListMap.get(nameLower);
        if (headerValueList == null) {
            return null;
        }
        return headerValueList.get(0);
    }

    public synchronized void addHeader(String name, String value) {
        String nameLower = name.toLowerCase(Locale.ENGLISH);
        List<String> headerValueList = headerNameToValueListMap.get(nameLower);

        if (headerValueList == null) {
            headerValueList = new ArrayList<>();
            headerNameToValueListMap.put(nameLower, headerValueList);
        }

        headerValueList.add(value);
    }

    /**
     * A simple parser intended to parse sequences of name/value pairs.
     * <p>
     * Parameter values are expected to be enclosed in quotes if they
     * contain unsafe characters, such as '=' characters or separators.
     * Parameter values are optional and can be omitted.
     * <p>
     * <p>
     * <code>param1 = value; param2 = "anything goes; really"; param3</code>
     * </p>
     */
    static class Parser {

        /**
         * String to be parsed.
         */
        private char[] chars = null;

        /**
         * Current position in the string.
         */
        private int pos = 0;

        /**
         * Maximum position in the string.
         */
        private int len = 0;

        /**
         * Start of a token.
         */
        private int i1 = 0;

        /**
         * End of a token.
         */
        private int i2 = 0;

        /**
         * Whether names stored in the map should be converted to lower case.
         */
        private boolean lowerCaseNames = false;


        /**
         * Are there any characters left to parse?
         *
         * @return <tt>true</tt> if there are unparsed characters,
         * <tt>false</tt> otherwise.
         */
        private boolean hasChar() {
            return this.pos < this.len;
        }

        /**
         * A helper method to process the parsed token. This method removes
         * leading and trailing blanks as well as enclosing quotation marks,
         * when necessary.
         *
         * @param quoted <tt>true</tt> if quotation marks are expected,
         *               <tt>false</tt> otherwise.
         * @return the token
         */
        private String getToken(boolean quoted) {
            // Trim leading white spaces
            while ((i1 < i2) && (Character.isWhitespace(chars[i1]))) {
                i1++;
            }
            // Trim trailing white spaces
            while ((i2 > i1) && (Character.isWhitespace(chars[i2 - 1]))) {
                i2--;
            }
            // Strip away quotation marks if necessary
            if (quoted
                    && ((i2 - i1) >= 2)
                    && (chars[i1] == '"')
                    && (chars[i2 - 1] == '"')) {
                i1++;
                i2--;
            }
            String result = null;
            if (i2 > i1) {
                result = new String(chars, i1, i2 - i1);
            }
            return result;
        }

        /**
         * Tests if the given character is present in the array of characters.
         *
         * @param ch      the character to test for presense in the array of characters
         * @param charray the array of characters to test against
         * @return <tt>true</tt> if the character is present in the array of
         * characters, <tt>false</tt> otherwise.
         */
        private boolean isOneOf(char ch, final char[] charray) {
            boolean result = false;
            for (char element : charray) {
                if (ch == element) {
                    result = true;
                    break;
                }
            }
            return result;
        }

        /**
         * Parses out a token until any of the given terminators
         * is encountered.
         *
         * @param terminators the array of terminating characters. Any of these
         *                    characters when encountered signify the end of the token
         * @return the token
         */
        private String parseToken(final char[] terminators) {
            char ch;
            i1 = pos;
            i2 = pos;
            while (hasChar()) {
                ch = chars[pos];
                if (isOneOf(ch, terminators)) {
                    break;
                }
                i2++;
                pos++;
            }
            return getToken(false);
        }

        /**
         * Parses out a token until any of the given terminators
         * is encountered outside the quotation marks.
         *
         * @param terminators the array of terminating characters. Any of these
         *                    characters when encountered outside the quotation marks signify the end
         *                    of the token
         * @return the token
         */
        private String parseQuotedToken(final char[] terminators) {
            char ch;
            i1 = pos;
            i2 = pos;
            boolean quoted = false;
            boolean charEscaped = false;
            while (hasChar()) {
                ch = chars[pos];
                if (!quoted && isOneOf(ch, terminators)) {
                    break;
                }
                if (!charEscaped && ch == '"') {
                    quoted = !quoted;
                }
                charEscaped = (!charEscaped && ch == '\\');
                i2++;
                pos++;

            }
            return getToken(true);
        }

        /**
         * Returns <tt>true</tt> if parameter names are to be converted to lower
         * case when name/value pairs are parsed.
         *
         * @return <tt>true</tt> if parameter names are to be
         * converted to lower case when name/value pairs are parsed.
         * Otherwise returns <tt>false</tt>
         */
        public boolean isLowerCaseNames() {
            return this.lowerCaseNames;
        }

        /**
         * Sets the flag if parameter names are to be converted to lower case when
         * name/value pairs are parsed.
         *
         * @param b <tt>true</tt> if parameter names are to be
         *          converted to lower case when name/value pairs are parsed.
         *          <tt>false</tt> otherwise.
         */
        public void setLowerCaseNames(boolean b) {
            this.lowerCaseNames = b;
        }

        /**
         * Extracts a map of name/value pairs from the given string. Names are
         * expected to be unique. Multiple separators may be specified and
         * the earliest found in the input string is used.
         *
         * @param str        the string that contains a sequence of name/value pairs
         * @param separators the name/value pairs separators
         * @return a map of name/value pairs
         */
        public Map<String, String> parse(final String str, char[] separators) {
            if (separators == null || separators.length == 0) {
                return new HashMap<>();
            }
            char separator = separators[0];
            if (str != null) {
                int idx = str.length();
                for (char separator2 : separators) {
                    int tmp = str.indexOf(separator2);
                    if (tmp != -1 && tmp < idx) {
                        idx = tmp;
                        separator = separator2;
                    }
                }
            }
            return parse(str, separator);
        }

        /**
         * Extracts a map of name/value pairs from the given string. Names are
         * expected to be unique.
         *
         * @param str       the string that contains a sequence of name/value pairs
         * @param separator the name/value pairs separator
         * @return a map of name/value pairs
         */
        public Map<String, String> parse(final String str, char separator) {
            if (str == null) {
                return new HashMap<>();
            }
            return parse(str.toCharArray(), separator);
        }

        /**
         * Extracts a map of name/value pairs from the given array of
         * characters. Names are expected to be unique.
         *
         * @param charArray the array of characters that contains a sequence of
         *                  name/value pairs
         * @param separator the name/value pairs separator
         * @return a map of name/value pairs
         */
        public Map<String, String> parse(final char[] charArray, char separator) {
            if (charArray == null) {
                return new HashMap<>();
            }
            return parse(charArray, 0, charArray.length, separator);
        }

        /**
         * Extracts a map of name/value pairs from the given array of
         * characters. Names are expected to be unique.
         *
         * @param charArray the array of characters that contains a sequence of
         *                  name/value pairs
         * @param offset    - the initial offset.
         * @param length    - the length.
         * @param separator the name/value pairs separator
         * @return a map of name/value pairs
         */
        public Map<String, String> parse(final char[] charArray, int offset,
                                         int length, char separator) {
            if (charArray == null) {
                return new HashMap<>();
            }

            HashMap<String, String> params = new HashMap<>();
            this.chars = charArray;
            this.pos = offset;
            this.len = length;

            String paramName;
            String paramValue;

            while (hasChar()) {
                paramName = parseToken(new char[]{'=', separator});

                paramValue = null;
                if (hasChar() && (charArray[pos] == '=')) {
                    pos++; // skip '='
                    paramValue = parseQuotedToken(new char[]{
                            separator});

                    if (paramValue != null) {
                        try {
                            paramValue = MimeUtility.decodeText(paramValue);
                        } catch (UnsupportedEncodingException e) {
                            // let's keep the original value in this case
                        }
                    }
                }
                if (hasChar() && (charArray[pos] == separator)) {
                    pos++; // skip separator
                }
                if ((paramName != null) && (paramName.length() > 0)) {
                    if (this.lowerCaseNames) {
                        paramName = paramName.toLowerCase(Locale.ENGLISH);
                    }

                    params.put(paramName, paramValue);
                }
            }
            return params;
        }

    }
}
